In U.S. Pat. Nos. 5,896,713 and 6,035,593, both of which are owned by the same assignee as is the present invention and both of which are incorporated herein by reference, tubular skylights are disclosed. Both of the skylights can use the skylight dome disclosed in U.S. Pat. No. 5,896,712 also owned by the same assignee as is the present invention and also incorporated herein by reference. These inventions represent advances over the prior art and one or more of them has found commercial success.
Briefly, a tubular skylight such as those mentioned above includes a tube assembly mounted between the roof and ceiling of a building. The top end of the tube assembly is covered by a roof-mounted dome or cover, such as the one disclosed in the above-mentioned '712 patent, while the bottom end of the tube assembly is covered by a ceiling-mounted diffuser plate. With this combination, natural light external to the building is directed through the tube assembly into the interior of the building to illuminate the interior.
The present invention has recognized that to optimize the light transmission into the building, the internal cylindrical surface of the tube assembly should be highly reflective. As understood by the present invention, one way to render a skylight tube assembly internally reflective is to laminate a reflective film onto the inside of the tube assembly or polish the inside of the assembly. With such a surface, the amount of light entering the dome that reflects off the tube walls as it propagates to the diffuser plate is maximized.
As understood herein, as the light is reflected through the tube assembly, focal points can form in the downwardly reflected light exiting the tube assembly. As further recognized by the present invention, the reflected light can become so intensely focused that it can damage the diffuser. Moreover, the diffuser is, at certain times, unable to diffuse all of the focal points in the reflected light exiting the tube assembly. These un-diffused focal points result in “hot spots” in the room sought to be lighted, i.e., bright spots, that appear on the walls, floor, etc. of the room in which the tubular skylight is installed. The present invention recognizes, however, that the light can be diffused within the tube assembly prior to reaching the diffuser so that the focal points are reduced.